The invention relates to a hybrid gas generator.
Conventional hybrid gas generators comprise an elongated cylindrical outer housing, a pressure chamber that is filled with pressurized gas and that is closed off by a membrane provided on the end face of the pressure chamber, a pyrotechnical propellant charge that is provided for opening the membrane and is accommodated in a preferably bushing-shaped propellant charge housing, the latter being connected to the outer housing at a location outside of the pressure chamber and the longitudinal axis of the propellant charge housing extending at a right angle to the longitudinal axis of the outer housing, and an axial outflow opening situated at one axial end of the outer housing.
Such gas generators are used, for example, to inflate an airbag or to actuate a belt tensioner. Due to the axial outflow opening on the end face, the radial construction space is kept small in comparison to generators with radial outflow openings.
The invention provides a hybrid gas generator that is configured simply and that stands out for its small radial construction space. According to the invention, the hybrid gas generator comprises an elongated cylindrical outer housing having a longitudinal axis, and a pressure chamber that is filled with pressurized gas and that is closed off by a membrane provided on an end face of the pressure chamber. The gas generator further comprises a pyrotechnical propellant charge that is provided for opening the membrane and is accommodated in a preferably bushing-shaped, separate propellant charge housing. The propellant charge housing is connected to the outer housing at a location outside of the pressure chamber and a longitudinal axis of the propellant charge housing extends at a right angle to a longitudinal axis of the outer housing. The generator also has an axial outflow opening situated at one axial end of the outer housing. The outer housing has a circumferential wall with a radial insertion opening for introducing the propellant charge housing. The propellant charge housing is attached to a section of the circumferential wall diametrically opposite the insertion opening in such a way that the propellant charge housing is secured at least against a movement in the direction of the longitudinal axis of the outer housing. With the hybrid gas generator according to the invention, the bushing-shaped propellant charge housing is radially inserted completely into the outer housing until it comes to lie against the section opposite the insertion opening, where it is secured such that it cannot be moved in lateral direction by the gas when the latter flows out. When the pressure chamber opens, the gas then flows laterally along the propellant charge housing, between the latter and the outer housing, towards the axial outflow opening. Since the propellant charge housing is inserted almost completely into the outer housing, it only protrudes slightly from it, which saves construction space. Furthermore, the attachment to the circumferential wall firmly secures the propellant charge housing which is then locked in two places, namely, in the area of the edge of the insertion opening and on the opposite section of the circumferential wall. The propellant charge housing is attached to the section of the circumferential wall by means of a form-fitting or a frictional fitting connection, by gluing or by welding, as a result of which there is no need for complex fastening means such as threaded connections or the like.
The edge of the radial insertion opening is configured as a cylindrical guide neck, which improves the positional stability of the propellant charge housing, especially until it has been attached to the section of the circumferential wall.
The propellant charge housing preferably has an end wall with which it lies against the circumferential wall and where it is attached to the latter. In the propellant charge housing, there are provided an igniter and an additional propellant charge. During combustion, the additional propellant charge produces hot gas that can mix with the cold pressurized gas.
The propellant charge housing has at least one opening oriented towards the membrane and, through this opening, combustion products are intentionally directed towards the membrane in order to destroy it in a predictable manner.